The present study on blood-material interactions focuses on the problem of calcium deposition on the polymer surface which develops during long term implantation of cardiac prosthesis resulting in eventual failure of the device. The axisymmetric type left ventricular assist device, comprised of a Biomer bladder, designed by Thermo Electron Corp., has been studied extensively. Calcification occurs most rapidly on Biomer conventionally flocked with polyethylene terephlalate, less severely on smooth and integrally textured Biomer surfaces and sparsely on cell seeded surfaces. In all examples, calcification is initiated on the bladder surface beneath the formed pseudoneointima (PNI) and not on the blood contacting surface. The inflow and outflow junctions and flexing areas of the pumping bladder are the major sites for calcification. Anticoagulation of the animal does not have a significant effect on calcium deposition but does limit the formation of a loosely adherent PNI. Light and electron microscopy indicate that crenated red blood and white cells become entrapped in PNI. Numerous giant cells are found in areas of calcification. Biochemical analysis of calcified plaque demonstrates the presence of two calcium binding amino acids, O-phosphoserine (O-P-Ser) and gamma-carboxyglutamic acid (Gla). The O-P-Ser most likely arises from fibrin and by radio-immunoassay, the Gla protein of bone, osteocalcin, was identified. Disc gel and serum immunoelectrophoresis demonstrated three components, albumin, and a protein in gamma-globulin and beta globulin regions. The protien in the beta-globulin region binds Ca 45. Presently, emphasis is being placed on the identification of circulating serum components which initially adsorb to the Biomer surface and modification of the blood contacting surface to alter the events which lead to calcification.